1. Field of the Invention
The present invention relates to an oil-retaining bearing structure for use in a rotary machine such as an axial-flow fan and others.
2. Description of the Related Art
In an axial-flow fan having a prior art sintered oil-retaining bearing, a stator is secured to a casing; a sintered oil-retaining bearing is secured to the stator; a rotating shaft is rotatably supported on the sintered oil-retaining bearing; a rotor is secured on the rotating shaft; and a fan is secured on the rotor. In addition, a thrust spacer is secured on the rotating shaft, in contact with an end face of the sintered oil-retaining bearing. Furthermore, a plate member is secured on the stator to thereby form a space, which is enclosed on the plate member side of the sintered oil-retaining bearing.
In such an oil-retaining bearing structure of the axial-flow fan, when the fan secured on the rotor rotates and a reaction force acts on the rotating shaft, the thrust spacer is pressed against the end face of the sintered oil-retaining bearing. Therefore a sliding sound occurs in the sliding surface between the thrust spacer and the end face of the sintered oil-retaining bearing. Also the thrust spacer is worn, reducing the life of the sintered oil-retaining bearing. Furthermore, since there is formed the space enclosed on the plate member side of the sintered oil-retaining bearing, the pressure will increase with a temperature rise in the enclosed space when the fan rotates, causing a lubricating oil retained in the sintered oil-retaining bearing to pass between the sintered oil-retaining bearing and the rotating shaft, flowing out to the opposite side of the plate member side of the sintered oil-retaining bearing. The lubricating oil thus flowing out is scattered out by a centrifugal force with the rotation of the rotating shaft, then passing between the stator and the rotor to leak outwardly, thereby shortening the life of the sintered oil-retaining bearing structure and smearing the exterior with the lubricating oil.